The present invention generally relates to color video signal recording and/or reproducing systems. A luminance signal of a composite color video signal comprises the luminance signal and a carrier chrominance signal, which are frequency-modulated. The carrier chrominance signal is frequency-converted into a band which is lower than the band of the frequency-modulated luminance signal. The frequency-modulated luminance signal and the frequency-converted carrier chrominance signal are superimposed and recorded, and then they are reproduced. More particularly, the present invention relates to a system which also records and/or reproduces the luminance signal which originally exists in a band that is identical to the band of the carrier chrominance signal, with the same phase as the luminance signal which exists outside the band of the carrier chrominance signal.
Conventionally, in a portable type color video signal recording and/or reproducing apparatus for home use, a so-called low-band-conversion system (a system in which the carrier chrominance signal is frequency-converted into a lower frequency band, and in the present application, the carrier chrominance signal thus frequency-converted into the lower frequency band will be referred to as a low-band-converted carrier chrominance signal) is used so as to effectively record and/or reproduce the color video signal, since the band in which recording and/or reproduction can be performed in the above portable type apparatus is narrow. In this low-band-conversion system, a luminance signal within a band excluding that of the carrier chrominance signal is extracted from a composite color video signal consisting of the luminance signal and the carrier chrominance signal and frequency-modulated. Moreover, the carrier chrominance signal is extracted from the above composite color video signal and frequency-converted into a band lower than that of the frequency-modulated luminance signal. These frequency-modulated luminance signal and frequency-converted carrier chrominance signal are superimposed, and then recorded and reproduced. A color video signal recording and reproducing system using the above low-band-conversion system is described in detail, in a U.S. Pat. No. 3,715,468 in which the assignee is the same as that of the present application.
In the composite color video signal, the carrier chrominance signal exists at a high frequency part of the luminance signal by use of frequency interleaving system. Hence, the luminance signal exists within a band of the carrier chrominance signal which is frequency-converted and recorded and reproduced. According to the conventional system, when the frequency of the carrier chrominance signal which is frequency-converted into the low band is returned to the original frequency (3.58 MHz in the case of the NTSC system) in the reproducing system, a signal for frequency-conversion obtained from a local oscillator is used. This local oscillator accurately produces a signal having a constant frequency.
However, when recording and reproducing a signal onto and from a magnetic tape, time base error is generally introduced due to wow and flutter in the magnetic tape travel. Accordingly, the demodulated luminance signal includes time base error, and the phase of the demodulated luminance signal and the phase of the luminance signal within the band of the restored carrier chrominance signal which is frequency-converted, does not become matched. Hence, the luminance signal within the band of the carrier chrominance signal does not contribute to the improvement of the resolution, and the resolution is determined by the luminance signal which is recorded and reproduced in the above band-limited state. Therefore, the luminance signal is not used effectively in the conventional system, and there was a disadvantage in that the resolution is inferior.